FMCW Automotive Radar Incorporating Nonlinear Frequency Hopping Sequence Of Fractional Bandwidth Multiband Chirps

Abstract

A novel and useful system and method by which radar angle and range resolution are significantly improved without increasing complexity in critical hardware parts. A multi-pulse methodology is described in which each pulse contains partial angular and range information consisting of a portion of the total CPI bandwidth, termed multiband chirp. Each chirp has significantly reduced fractional bandwidth relative to monoband processing. Each chirp contains angular information that fills only a portion of the ‘virtual array’, while the full virtual array information is contained across the CPI. This is done using only a single transmission antenna per pulse, thus significantly simplifying MIMO hardware realization, referred to as antenna-multiplexing (AM). Techniques for generating the multiband chirps as well as receiving and generating improved fine range-Doppler data maps. A windowing technique deployed in the transmitter as opposed to the receiver is also disclosed.

Description

FIELD OF THE DISCLOSURE[0001]The subject matter disclosed herein relates to the field of imaging radar, sonar, ultrasound, and other sensors for performing range measurement via FMCW signals and / or angle measurement via digital beam forming and array processing and more particularly relates to a system and method of FMCW radar that utilizes a nonlinear sequence of fractional bandwidth time multiplexed FMCW signals and related range and Doppler processing.BACKGROUND OF THE INVENTION[0002]Recently, applications of radars in the automotive industry have started to emerge. High-end automobiles already have radars that provide parking assistance and lane departure warning to the driver. Currently, there is growing interest in self-driving cars and it is currently considered to be the main driving force in the automotive industry in the coming years.[0003]Self-driving cars offer a new perspective on the application of radar technology in automobiles. Instead of only assisting the driver, ...

AI Technical Summary

Benefits of technology

This patent describes a technique for improving the performance of a MIMO radar system by using partial angular information and a windowing technique. This technique involves transmitting pulses with only a portion of the virtual array information and then using a window function in the transmitter to improve sidelobe performance without affecting Doppler data processing. The technical effects of this technique are simplified MIMO hardware realization and improved sidelobe performance.

Problems solved by technology

Besides cameras and ultrasonic sensors, car manufacturers are turning to radar as the cost of the associated technology decreases.

Visual sensors are also degraded by bad weather and poor visibility (e.g., fog, smoke, sand, rain storms, snow storms, etc.).

They are also limited in estimating radial velocities.

These, however, are expensive, as most have moving parts and very limited range.

The reception of foreign signals (interference) can lead to problems such as ghost targets or a reduced signal-to-noise ratio.

On the contrary, safety functions of future systems require very low failure rates.

Therefore, radar-to-radar interference is a major problem in radar sensor networks, especially when several radars are concurrently operating in the same frequency band and mutually interfering with each another.

As stated supra, a major challenge facing the application of automotive radar to autonomous driving is the highly likely situation where several unsynchronized radars, possibly from different vendors, operate in geographical proximity and utilize overlapping frequency bands.

Note that the currently installed base of radars cannot be expected to synchronize with new automotive radar sensor entrants, nor with any global synchronization schemes.

Achieving a high resolution simultaneously in the angular, range and doppler dimensions is a significant challenge due to (inter alia) a linear increment in hardware complexity resolution.

One problem that arises in radar systems is known as range cell migration (RCM) in which the calculated range bin of the radar return signal migrates over time (i.e. slow time) due to the velocity of the target.

For large enough chirp bandwidths, however, RCM may become a problem for sufficiently fast targets or ego velocity.

Another problem that arises is the ambiguity between Doppler velocity and range (described supra) where the peaks for two targets with different velocity and range can occur at the same position in certain conditions, i.e. the target range and velocity are calculated using information from the peak position and the phase difference between the peaks.

This will lead to wrong or missed detections.

Yet another issue concerns range resolution where the higher chirp bandwidth, the better the range resolution.

Higher chirp bandwidth, however, presents its own problems in that the complexity and cost for circuitry in the receiver at higher bandwidths is significantly higher.

Images